On Sat, 14 Apr 2018 13:42:27 -0700 (PDT), John-Del
wrote:

I have this device which uses 14 AA rechageable batteries.

There's quite a bit on charging Eneloop cells he
https://eneloop101.com
https://eneloop101.com/charge/
Plenty of warnings to NOT use really fast chargers and really dumb
(trickle) chargers.

Can I suggest yet another alternative? 14 NiCd cells, at 1.35v each =
18.9V total. If you replace the AA cells with five 14500 LiIon cells,
which are the same physical size, that would be:
5 * 3.6 = 18.0v
There are plenty of smart chargers available for the RC market that
can deal with a 5s battery pack. I have one of these:
https://hobbyking.com/en_us/imax-b6-50w-5a-charger-discharger-1-6-cells-genuine.html
Checking the specs, it charge 1 to 6 cells so it should work.
If you need AC power, LiFePO4 charging, PC connectivity, upgradeable
firmware, and terminal voltage adjust, the V2 version is what you
want:
https://hobbyking.com/en_us/imax-b6ac-v2-professional-balance-charger-discharger.html

I use nothing by the cheapest cells, which sucks because they usually
only have about half the capacity and lifetime of a decent cell.
However, they're cheap, and my use in mostly flashlight is not
critical.
https://www.ebay.com/sch/Rechargeable-Batteries/48619/i.html?_nkw=14500+li-ion+battery
I haven't tried this brand, but at $1/ea, it's worth trying.

One potential problem with LiIon is if your unspecified device runs on
+10 and -10 volts. 5 cells won't work but 6 cells might. It all
depends on the operating voltage range of your unspecified device and
on how it's wired/designed/configured.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558